In a conventional gas-insulated switchgear, in order to electrically insulate between a pressure tank for encapsulating insulation gas, such as dry air, and a conductor on which a high voltage is applied, an insulation capability is maintained in such a way that insulation gas is encapsulated at about 0.4 to 0.5 MPa-(G) of gas pressure (index (G) indicates an atmospheric-pressure basis), and an insulation material, such as an epoxy resin, is coated around a conductor (for example, refer to Patent Document 1).
Moreover, there is a well-known gas-insulated switchgear in which an insulation capability is maintained in such a way that insulation gas is encapsulated at low gas pressure in a pressure tank, and an epoxy-resin insulator covering a central conductor is disposed at a position at which a distance between the pressure tank and the central conductor of a bushing is short (for example, refer to Patent Document 2).